3 days will not be enough! 
Ciao Fiorina!
All of Elba is beautiful, I cannot begin to think of any place I'd say to stay away from ;-) Of course, the port towns of
Portoferraio and
Porto Azzurro have their own charm and their own attractions but might be considered "less" nice if one is solely thinking of beaches ;-). There are beaches nearby but mostly made of small rocks or reef.
Elba has all kinds of beaches, from sandy beaches to small pebbles to larger rocks to reef... most are small beaches in the small coves that surround all of the island. Early June is still early season for Elba so I am not sure if the water will be warm enough for bathing but you can surely enjoy getting some sun in mornings or afternoons.
The southern area of the island is where most of the sandy beaches are located, in the bay in
Marina di Campo (seen as Campo nell'Elba on Google maps) and
Lacona. This is also where you'll find many campsites and hotels with bungalows (keep in mind many "residences" are just that, but the name can be misleading). You can look at places to stay in and
near Lacona here and in
Campo nell'Elba here.
How much
hiking would you like to do? When you arrive in Elba, find yourself a map for the island for hiking (1:25000). Two favorites trails I recommend are both in the western part of the island on
Monte Capanne:
- the first is from Marina di Campo - head to
San Piero in Campo. Park and follow signs to the "campo sportivo" (the soccer field). From here, follow CAI path#7 (CAI trails are always marked with red and white paint and maintained by local sections of the association), then 34 and 30. These take you past the "
caprili", the ancient stone huts (the mountain is granite here, you'll find it everywhere you go) used by the goat herders in the mountain. Very beautiful! Also beautiful views of the island, coast, other islands in the archipelago and on clear days, you can see Corsica. Entire route is about 10-12 km, depends how far you go. We followed #8 at the end to arrive to the last caprile and had lunch there, then went back - a whole day out but we headed out late.
- the second one is also on Monte Capanne but from the north side: head to
Marciana and take trail #1 up to the peak of
Monte Capanne. Really beautiful views!! If you're tired once you reach the peak, you could take the cable car back down to Marciana.
We had terrific seafood wherever we were and stopped for food so I am not sure I can recommend one single place. Just head to where your sight and nose leads you
We were near Marina di Campo so we highly recommend the area.
